Food Science and Technology Project Topics

Nutritional Composition and Antimicrobial Activities of Peels of Some Selected Fruits and Vegetables (Plantain (Musa Spp) and Pawpaw (Carica Papaya))

Nutritional Composition and Antimicrobial Activities of Peels of Some Selected Fruits and Vegetables (Plantain (Musa Spp) and Pawpaw (Carica Papaya))

Nutritional Composition and Antimicrobial Activities of Peels of Some Selected Fruits and Vegetables (Plantain (Musa Spp) and Pawpaw (Carica Papaya))

Chapter One

The Objective of the Study

The aim of this study is to determine the nutritional composition and anti-microbial activities of different peels of vegetables and fruits (pawpaw and plantain).




Plantain belongs to the genus Musa of the family musaceae.  Nearly all edible plantain cultivar are derived from two wild species, M. acuminate and M. balbisiana (Robinson, 1996).  These wild species are classified on the basis of the proportion of the genetic constitution contributed by each parental source (Robinson, 1996). Plantain is a staple crop and an important dietary source of carbohydrate in Nigeria and in the humid tropical zones of Africa, Asia and South America (Robinson, 1996).  Plantain is rich in vitamins A, C and B group as well as minerals such as calcium and iron (Marriott and Lancaster, 2003; Robinson, 1996).  Plantain provides between 9% and 35% of the total calories in the diets of more than 14 million people in Sub sahara Africa (Robinson, 1996).  The contributions of this staple starch crop to the food chains of this region cannot be overemphasized (Robinson, 1996).

Plantains are typical climacteric fruits in that they exhibit a well-defined pre-climacteric phase after harvesting during which the fruit remains unripe, the basal respiration rate is low and ethylene production is almost undetectable.  The respiratory climacteric commences spontaneously and there is a rapid and well-defined rise in respiratory rate which is closely synchronized with evolution of ethylene, with chlorophyll breakdown in the peel and with starch to sugar conversion and tissue softening in the pulp (Marriot and Lancaster, 2003; Ogazi, 1996).  The fruit usually harvested at its mature but unripe stage, ripens within two to seven days, thus making plantain a highly perishable crop, particularly in the overripe stage (Robinson, 1996). An unripe plantain and the plantain have high starch and low sugar levels plus copious amounts of bitter-tasting latex. Starch is converted to sugar as the fruit ripens, so that plantains can eventually contain about 25% of total sugars. As the plantain ripens, the latex is also decomposed. Plantain has the stinging, bitter latex, so the peel is removed with a knife and the pulp is soaked in salt water for 5–10 min prior to cooking. Plantains are harvested unripe and green, because they can ripen and spoil very rapidly (Daniells et al., 2001).

FAO (2004) data sources put the world production of plantains at about 60 million tons (FAO, 2004).  In West Africa, plantain production increased at an average annual rate of between 2.3% to 2.6% (FAO, 2004). The level of production of plantains in Africa is comparable with other fruits like grapes (57 million tons); citrus (50 million tons) but much greater than most other important fruits like apples (21 million tons) and mangoes (13 million tons) (FAO, 2004).  The higher production figures for plantains has been attributed  to the cheaper methods of growing that require few labor inputs, little soil preparation and little weeding are needed once the plant has established vegetative cover (FAO, 2004).

 Maturity Indices of Musa spp

Plantain require about three months from the beginning of flowering until harvest.  Multiple fruits are produced on a large bunch, weighing between 50-200kg (Ogazi, 1996).  Within the bunch are clusters of double rows of fruit called “hands” and individual fruit called “fingers” (Ogazi, 1996).

Maturity standards for plantains are less precise than they are for plantains.  Several different external and internal fruit characteristics can be used to determine plantain maturity.  These include fruit diameter, age of the bunch, angularity of the fruit, length of the fruit, and peel color (Johnson et al., 1998).  The stage of maturity for harvest depends on the intended market destination (Johnson et al., 1998).  Locally marketed plantains can be harvested at a more advanced maturity stage compared to export market fruit.  Export market destined fruit should be harvested the day before or the same day of shipment (Ogazi, 1996).  Plantain maturity is related to the diameter of the fingers.  This is determined by measuring the diameter of the fruit at its mid-point with a pair of calipers (Ogazi, 1996).

Another method for estimating plantain maturity is to record the age of the bunch.  The time from when the fruit bunch first becomes visible (Shooting) is recorded.  Bunches can be tagged with different colored ribbons at the time of shooting, and subsequently harvested after the appropriate time for the particular cultivar, based on the season of the year and experience (Johnson et al., 1998).  The colour of the ribbons is changed weekly to coincide with the time of shooting and subsequently the age of the bunch (Johnson et al., 1998).

A third method used to determine harvest maturity is to observe the shape (fullness) and angularity of the fruit.  Immature fruit is angular in cross-sectional shape and has distinct ridges (Ogazi, 1996).  As the fruit matures, it becomes less angular and more rounded or full.  The degree of roundness differs between cultivars and location of the hand on the bunch.  Typically, the fullness of the fruit on the middle hand is measured.  The appropriate shape to harvest the fruit depends on the market destination.  Fruit intended for the domestic market should be harvested when the fruit shape is nearly round (Johnson et al., 1998).

A fourth way of estimating plantain bunch maturity is to measure the length of the edible pulp portion of the fruit from the fingers in the middle hand.  The length should be a minimum of 15cm for the domestic market and 18cm for the export market (Johnson et al., 1998).  Finally, peel color is another frequently used method of assessing fruit maturity.  The peel remains green throughout growth and development of the fruit until it reaches physiological maturity.  It then changes to a yellow color during ripening (Ogazi, 1996).

However, plantain fruit should be harvested when the peel is green in color to withstand the rigors of handling and distribution (Johnson et al., 1998).  Internal fruit composition changes dramatically during plantain fruit ripening.  At physiological maturity, the fruit is fully developed in size, green in peel color, and at its highest level of starch (Ogazi, 1996).  The starch will progressively be converted to sugar as ripening progresses.

The stage of harvest maturity of plantains will depend on the target market.  Plantains for local market are harvested at a more advanced stage of maturity than those for exportation (Ogazi, 1996).  However, if the fruit is too mature at harvest, particularly following irrigation or rainfall, fruit splitting can occur during handling.  Also, mature fruit may ripen prematurely during transport or storage (Ogazi, 1996).




  Collection of Plant Materials

Unripe Pawpaw (Carica papaya) and unripe plantain (Musa spp) was purchased from “Oja Oba”. The pawpaw and plantain was peeled using knife and sundried for four days. It was prepared in the department of Food Science and Technology, Rufus Giwa Polytechnic, Owo, before it was transferred to the laboratory for analysis.

   Sterilization of Materials

All glass wares were washed with detergent and rinsed with distilled water properly. These were then air dried before wrapping with aluminum foil and sterilized in hot air oven at 170oC for 2hours. Prepared media such as nutrient agar and nutrient broth were sterilized in an autoclave at 121oC for 15minutes. Cork borer, glass rods and forceps were sterilized by dipping in 70% ethanol which was then flamed in Bunsen flame. The inoculating loop was also sterilized by heating in Bunsen flame. The inoculating loop was also sterilized by heating to redness using naked flame before and after each use.




Table 3: Anti-bacterial activities of Fruits and Vegetables extracts (Pawpaw and Plantain)





From the above study it can be concluded that plantain a vegetable plants is one of the important plant cultivated in African especially in Nigeria, the results for proximate shows that plantain contain about 11.5% of fat, 10.85% of protein and 49.35% of carbohydrates, theses value are relatively higher than that of pawpaw which have a value of 7% of fat, 8.8% of protein and 47.4% of carbohydrates. Though the ash content of plantain was low compared to pawpaw with a value 4% to 7.5%, meaning pawpaw is rich in minerals than plantain, from the study it was also noted that plantain contain higher moisture content than pawpaw. Both samples (plantain and pawpaw) are antibacterial active though plantain is more active against E. coli and Staphylococcus aureus than pawpaw while against Klebsiella pneumonia pawpaw is more active than plantain.


Since plantain has being shown to contain less protein (lesser than requirement value of protein in diet) but higher carbohydrates, it is recommended that plantain should be incorporated into other foods that are rich in protein such as beans. Since pawpaw had been revealed to be good source of dietary fiber it is therefore recommended that more of pawpaw (moderate form) should be consumed for it can help a long way in diabetes diseases and cardiovascular diseases.


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